Systemic Lupus Erythematosus (SLE) is an autoimmune arthritic disease of unknown etiology but behaves as an antigen-driven response to the nuclear component, U1 small nuclear ribonucleoprotein particle (U1snRNP). U1nsRNPs are highly conserved among eukaryotes but not thought to exist in prokaryotic organisms. However our work suggests that ribonucleoprotein particles displaying high homology to U1snRNPs do exist among eubacteria. As bacterial snRNPs could provide an antigenic stimulus which might lead to autoimmunity, a small group of SLE-susceptible MRL-lpr/lpr mice were injected with extracts from one of the "U1snRNP"-positive bacteria. The mice injected with bacterial extracts displayed early expression of certain clinical and immunological symptoms of SLE, commencing about two weeks after inoculation (mice were one month old at inoculation). This proposal intends to examine the details of this immune response through variations in immunization dose and time relevant to "natural" disease course and to include more thorough clinical, histopathological and immunological assessments of the outcomes. Clinical criteria will principally include assessments of arthritis, lymph node hyperplasia and alopecia; histopathological criteria will principally monitor tissue abnormalities in joints, kidneys and lymph nodes; and immunologic criteria will use ELISA reactivity to human nuclear extract and to bacterial extract for titers and isotypic profiles, direct immunofluorescence to detect glomerulonephritis, indirect immunofluorescence to detect reactivity to specific nuclear antigens, and western blotting to determine reactivity to U1snRNP-specific proteins MRL-lpr/lpr mice immunized with physiological saline and random genetic mice (Swiss-Webster) injected either the bacterial extract or saline will serve as experimental controls. Other candidate "U1snRNP"- containing bacterial organisms will be identified and/or evaluated using computer-based genomics, the polymerase chain reaction (PCR), northern hybridization and RNase protection assays, and mRNA splicing- complementation assays. Finally, the ability of these candidate prokaryotic cell extracts to stimulate SLE will be assessed by immunization of MRL-lpr/lpr mice and assessment of clinical, histopathological and immunological symptoms. The outcome of these experiments should provide a cleared indication of whether: inoculation with pro-karyotic cells; and these latter pro-karyotic cells can also stimulate SLE symptoms in MRL-lpr/lpr model mice. The possibility that bacteria are etiological agents of SLE unveils a wealth of antibiotic therapeutic opportunities for treatment of SLE or other autoimmune, rheumatological disorders.